Halak, 28, joins Braden Holtby in goal for Washington. He began the year with the St. Louis Blues, but was traded earlier this month to Buffalo. Halak started 38 games for St. Louis this season and appeared in 40. He had a .917 save percentage and a 2.23 goals-against average.

Of course, Halak has already played a prominent role in Caps history. His stunning play in the 2010 Stanley Cup playoffs helped the No. 8 seed Montreal Canadiens to a first-round series victory over the Caps, who had the best record in the NHL that year. In final three games of that series, Halak stopped 131 of 134 shots on goal.

After the trade by the Blues on Feb. 28, Halak never played a game for the Sabres. He has a salary-cap hit of $3.75 million, but is an unrestricted free agent after the season. Washington will likely recall Philipp Grubauer from AHL Hershey for its game tonight in Philadelphia.

Because the Caps were able to include Klesla in the trade with the Sabres, they are in relatively good shape with about $2.1 million of salary-cap space remaining. That would help if the organization still hopes to add top prospect Evgeny Kuznetsov, a Russian left wing whose contract in the KHL ends April 30th.